1. Field of the Invention
The present invention relates to a method for the correction of television signals at transmission as well as to a device for the implementation of this method.
2. Description of the Prior Art
The defects created during the transmission of television signals, such as the line tilt phenomenon or the linear distortion phenomenon generally cause no visible problems in reception in a standard television system. However, such defects may become very troublesome when the scrambling used is of the "line cut and rotate" type (where the line is permutated about a randomly determined point at which this line is cut, hereinafter called a "cut point"): these defects may greatly lower the quality of the unscrambled images.
The line tilt of a video signal is characterized by a tilt of a few per cent in this signal. For example, a video line with a constant luminance, normally represented by a horizontal line, is frequently a line that rises or descends slightly. This phenomenon may originate either in the transmission equipment or in the demodulator of the receiver.
The linear distortion generally takes the form of overshoots extending over the entire length of the line. This phenomenon has the same causes as the "line tilt".